Tapcensus

California

Contra Costa County drinking water quality

84 active public water systems serve 582,859 people in Contra Costa County. 63 are compliant, 21 had at least one EPA violation in the past three years, 0 are designated serious violators, and 8 carry a health flag.

Active systems 84 39 community systems
People served 583K by public water systems
Systems with violations 21 25% of active systems, past 3 years
Serious violators 0 8 systems carry a health flag

Needs attention

Orwood Resort CA0707545 · Community water system · Serves 350 2 rules violated in the past three years. Unresolved: Lead and Copper Rule and Lead and Copper Rule Revisions.
Oakley Mutual Water Company CA0706004 · Community water system · Serves 170 2 rules violated in the past three years. Unresolved: Lead and Copper Rule Revisions.
Russos Mobile Park CA0707601 · Community water system · Serves 110 2 rules violated in the past three years. Unresolved: Lead and Copper Rule and Lead and Copper Rule Revisions.
Sandmound Mutual CA0707556 · Community water system · Serves 100 2 rules violated in the past three years. Unresolved: Lead and Copper Rule and Lead and Copper Rule Revisions.
Bella Vista Water Sys CA0707589 · Community water system · Serves 93 3 rules violated in the past three years. Unresolved: Lead and Copper Rule and Lead and Copper Rule Revisions.
Canyon School CA0707620 · Non-Transient non-community system · Serves 80 1 rule violated in the past three years. Unresolved: Lead and Copper Rule Revisions.
Sandy Point Mobile Home Park CA0707597 · Community water system · Serves 67 2 rules violated in the past three years. Unresolved: Lead and Copper Rule and Lead and Copper Rule Revisions.
Colonia Santa Maria CA0707517 · Community water system · Serves 32 2 rules violated in the past three years. Unresolved: Lead and Copper Rule and Lead and Copper Rule Revisions.

Community water systems

39 systems, largest first
SystemServesStatusRules violated, 3 yrUnresolved
Contra Costa Water District
 210,500 0 0
City of Antioch
Antioch 		116,781 0 0
Brentwood
Brentwood 		64,513 0 0
City of Pittsburg
Pittsburg 		62,500 0 0
Diablo Water District
 47,158 0 0
City of Martinez
Martinez 		31,015 0 0
Golden State Water Company Bay Point
 23,765 0 0
Town of Discovery Bay
 16,790 0 0
Pleasantimes Mutual Water CO
 644 0 0
Clayton Palms Water
 549 1 1
Willow Mobile Home Park
 481 0 0
Willow Park Marina
 380 1 0
Orwood Resort
 350 2 2
Delta Mutual Water Company
 333 1 0
Riverview Water Association
 230 1 1
Camino Mobilehome
 210 0 0
Bethel Island Estates
 200 0 0
Bethel Island MHC
 185 0 0
Oakley Mutual Water Company
 170 2 1
Big Oak Mobile Home Park Water
 156 0 0
Farrar Park Property Owners
 140 0 0
Riverview Mobile Home Park
 126 1 1
Bethel Island Mutual Water CO
 123 1 1
Russos Mobile Park
 110 2 2
Sandmound Mutual
 100 2 2
Anglers Subdivision 4
 99 1 1
Bella Vista Water Sys
 93 3 2
Marina Mobile Manor
 75 0 0
Knightsen Community Water System
 73 0 0
Sandy Point Mobile Home Park
 67 2 2
Doubletree Ranch Water System
 66 0 0
Moraga Heights Mutual Water
 66 0 0
Angler S Ranch #3
 60 1 1
Dutch Slough Water Works
 49 1 1
Casa Medanos Water System
 45 1 1
Colonia Santa Maria
 32 2 2
Wilcox Station Ranch
 31 1 1
Randall-Bold Water Treatment Plant
 1 0 0
Ccwd/brentwood Wtp
 0 0 0
Non-community systems (45: schools, campgrounds, workplaces, restaurants)

These systems serve places people visit rather than homes.

SystemServesStatusRules violated, 3 yrUnresolved
Excelsior Middle School
 600 0 0
Mount Diablo State Park
 364 0 0
Knightsen Elementary School
 350 0 0
Byron Corners INC
 205 0 0
Country Junction Deli
 200 0 0
Dwr Delta Field Division Banks PP
 180 0 0
Los Vaqueros Marina Bldg
 180 0 0
Delta Sportsman
 150 0 0
Sugar Barge Marina
 150 0 0
Concord MT Diablo Trailride Assoc.
 120 0 0
Gas N Save
 120 0 0
Ebrpd Alhambra
 115 0 0
Ebrpd Bay Point Regional Shoreline
Pittsburg 		105 0 0
Bethel Market
 100 0 0
Delta Bar and Grill
 100 0 0
Ebrpd Round Valley Water System
 82 0 0
Canyon School
 80 1 1
New Life Marina
 80 0 0
Bethel Baptist Church
 75 0 0
Bridgehead Cafe
 75 0 0
Cruiser Haven Marina
 75 0 0
Old Borges Ranch Water Sys
 75 0 0
Ebrpd Black Diamond Mines
 74 0 0
Ebrpd Little Hills
 66 0 0
Wahl Family Water System
 65 0 0
Byron Inn
 60 0 0
Willow Pass Bussiness Park Water System
 60 1 1
Ebrpd Morgan Territory
 57 0 0
McAvoy Yacht Harbor
 55 0 0
Bethel Missionary Baptist
 54 0 0
Byron United Methodist
 50 0 0
Ebrpd Old Briones Regional Park
 47 0 0
Bethel Harbor
 45 0 0
Holland Riverside Marina
 45 0 0
Bay Standards
 41 1 1
Byron Airport
 35 0 0
Willowest Marina WS
 35 0 0
All Star Academy of Danville
 30 0 0
Brentwood Marina
 30 0 0
Los Vaqueros Interpretive Center
 30 0 0
Sunset Marina
 30 0 0
Wildwood Acres Resort
 28 0 0
Byron Roadhouse
 25 0 0
Marin Food Specialties
 25 0 0
Tess Farm Market
Brentwood 		25 0 0
Inactive systems (94, no longer operating or reporting)

Kept for the record and excluded from the county totals above. Browse inactive systems.

About this data

Totals cover active systems. Systems serving more than one county are counted in each county. EPA counts the rules a system was in violation of, not the individual violations; one rule can carry several.

Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The California records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet. Retrieved from ECHO on Oct 11, 2026.